1. Field of the Invention
The present invention relates to X-ray diagnostics installations, and in particular to such installations having an adjustable bed on which the examination subject is disposed and having an image intensifier video chain with image storage capability.
2. Description of the Prior Art
An X-ray diagnostics installation as described in German OS No. 31 47 128 wherein positioning of the examination subject to a desired position can be undertaken during radiation of the patient with X-rays (transillumination check). The screen of the visual display unit shows the transilluminated regions of the patient, and thereby enables constant checking of the positioning operation. In order to maintain the radiation dose to which the examination subject is exposed as low as possible, the transillumination check can be undertaken with an X-ray dose rate which, though not adequate for a diagnosis, is sufficient for adjustment of the position of the examination subject. Despite these measures, the examination subject is still exposed to a constant radiation dose during the transillumination check.
Constant irradiation of the examination subject during positioning could be avoided by employing a visual display means with an image storage, however, this procedure frequently requires making several exposures (stored shots) until the desired position of the examination subject is reached. This method therefore also requires exposing the patient to a radiation dose which is relatively high.